Method for making stereotype mats



Patented Jan. 27, 1925.

UNITED STATES I I 1,524,155 PATENT 'o FlcE.

ARLIE WILLIAM SCHORGER, OF MADISON. WISCONSIN, ASSIGNOR TO 0. 1*. BURGESS LABORATORIES, OF MADISON, WISCONSIN, A CORPORATION OF WISCONSIN.

METHOD FOR MAKING STEREOTYP E MATS.

1T0 Drawing.

To all whom it may camera:

Be it known that I. Anna WTLLTAM Sorroaonn. a citizen of the United, States, residing at Madison. in the county of Dane. State of Wisconsin, have invented certain new and useful Improvements in Methods for Making Stereotype Mats: and I do hereby declare the following to be a full, clear. and exact description of the invention, such as will enable other skilled in the art to which it appertains to make and use the same.

The rapidity with which modern newspapers are printed is due largely to use of the stereotype mat, also known as a matrix. or fiong. As soon as a form containing the type has been set up, a stereotype mat is superimposed, then covered with blankets or felts and passed through a rolling machine, whereby the mat requires a reverse impression of the type. The mat after drying is placed in a casting machine where it is held in the form of a cylinder. Molten' stereotype metal is now poured into the machine whereby a metal cylinder is obtained containing on its surface an exact duplicate of the type in the original flat form.

The cylindrical stereotype plate is then placed in a cylinder press whereby papers can be printed at high speed. Several casts can be made easily and rapidly from the same mat so that a number of presses can be placed in operation almost simultaneously.

There are two types of stereotype mats in commercial use, the so-called wet mat and the dry mat. The wet mat, which is in most extensive use, consists of two or three sheets of thin blotting paper and two to four sheets of tissue paper held together by a paste made of starch, dextrin, gum arabic, etc. The tissue is used on the face to obtain a sharp, smooth impression. The wet mat. after having been built up, must be stored in a wet condition. This is a serious objection. Furthermore, it must be dried on the type form as otherwise it would warp and shrink greatly. Considerable labor and much skill, judgment and experienoe is required to produce a satisfactory wet mat. The rush of work in a newspaper press room cannot tolerate unreliability 'in the quality of the mats supplied to the casting machine. Without suitable mats the printing cylinders cannot be made and with Application filed November 80, 1923. Serial No. 677,880.

out these the printing can not proceed. In a modern newspaper ofiice an interruption or even delay incident to bad workmanship on the wet mats, or unreliability in the starch with which they are made is a serious matter. They have to be made up shortly prior to the time fixed for their use and without adequate opportunity for testing, excepting by actual use. But by the time defects in material and workmanship develop, the harm has been done to the printer and to all those ramifications of the newspaper art which are dependent on the timely issuance of the paper from the press.

The dry mat on the other hand. can be stored in the dry state in any quantity. but previous to use must'be conditioned by being placed in a humidor where it takes up from 10 to of moisture. It is then rolled on the form, removed, placed in a cylindrical scorcher where most of the moisture is removed in one or two minutes. lit is then ready for use in the casting machine. From the standpoint of initial cost, speed, and ease of manipulation it is preferable to use a dry mat instead of a wet mat. In getting out a rush edition where every second counts. it is obvious that greater speed can be obtained with a dry mat.

The objection to the dry mat as now being manufactured is that it has a rougher surface ,thanthe wet mat and does not give satisfactory impressions with half-tone blocks with a fine screen, and in general. lacks sharpness of definition. The dry mat does not have the plasticity of a wet mat, so that fractures may be produced durin molding on the type. into which the molten stereotype metal will run. On removing the casting, the face of the mat will be torn so that the mat cannot be used for a second casting. A properly made mat should permit the making of 10 to 20 casts. The fractures and roughness characteristic of the present dry mat is largely due to the character of the fibers employed. If they are long and the surface roughens readily so that loose fibers are produced, the molten metal will flow amid the fibers, the surface of the mat becoming torn when the casting is removed, so that both the casting and the mat may be rendered useless.

It is not possible to obtain a satisfactory mat by the use of large quantities of adhesives, such as are frequently employed, ow-

ing to the fact that the mat when dry is not plastic, and if used wet it has all the disadvantages already pointed out.

\Vith my invention, as will be described below, these objections are overcome. by the use of relatively fine. short, soft fibers, formed into a sheet to give. an article having a high degree of smoothness, strength and im ressionability.

he natural cellulosic fibers available for manufacture of paper are so long and smooth that when a sheet formed from them is subjected to a strain, the fibers either slip past one another or are ruptured. In eithel case a roughness is produced that permits the metal to run into .tllB, mat. This difiiculty cannot be overcome by simply shortening the fibers by cutting, since, in this case the sheet would have very little strength. In my process these objections are overcome by cutting and splitting the fibers into fine fibrils. Rag stock, cotton linters. wood pulp and similar fibers, either alone or mixed, are placed in a papermakers heater, or other suit-able apparatus and while suspended in water are subjected to a cutting and splitting action by suitably adjusting the beater roll with respect to'thc bed plate. After suflicient beating, the original fibers will have been shortened in length and split longitudinally into small fibrils. The splitting action is complete in some fibers; in others the ends are separated into brushes and the fibrils formed on the sides of the fiber give an arborescent appearance. The difference between the fibers before and after beating cannot well be shown ina pen and ink drawing, but is readily apparent under a microscope, particularly, if the fibers are stained in well known manner. The relatively prolonged beating in water separates the fibres from one another by combing out the pulp and without undue cutting or breakage of the whole fibers develops the fibrillated condition so important to the successful practice of the present invention. When the fibers are combed out as described above and made into a sheet on the paper machine, the individual'fibers are so interlocked by reason of the fibrils that stick out along the sides and ends of the individual fibers that the sheet as a whole acts somewhat like a net permitting the required amount of stretching and plasticity during molding against the type, but with adequate strength to permit the sheet subsequently to be rolled into cylindrical form and with all the toughness and heat resistance needed for a. subsequent repeated contact with hot metal.

In beating the fibers to the necessary state of fibrillation they unavoidably become hydrated or gelatinized on the surface, some of the smaller fibers, or fibrils formed from them, may be completely converted to a structureless mass of gelantinized cellulose. Gelatinized cellulose per se has-the characteristic that when dried it hardens t6 a horn like mass. darkgray in color, and very hard and brittle. During the change tothe hard horny mas the shrinkage of the material .is enormous, and there is a pronounced tendency to warp and curl.

In beating the fibers, as above described, gelantinization occurs to such an extent that if the stock were made into a sheet and allowed to dry, the sheet would become hard and brittle and have a low receptivity to impression. I have found that by heating the pulp in an alkaline solution the gelatinized cellulose is destroyed. or removed, leavin behind clean ungelatinized fibrillated fibers of excellent felting properties and with no tendency to become hard or brittle on drying. The heating or cooking may be performed at atmospheric pressure or ata steam pressure of 5 to 20 ounds. The amount of chemical used an the cooking conditions employed will vary with the nature of the pulp. and the degree of beating. But with an easy-bleaching sulphite wood pulp. after fibrillationas described above, the alkaline cooking solution may properly contain 10% of caustic soda based on the weight of the pulp, and the cooking may be continued until the liquor is no longer alkaline to litmus. The resulting fibers, after washing with water. are unchanged in form, but are lighter in color, soften on drying and possessed of a high degree of plasticity when in sheet form. It will be course. that other alkalis and alkaline earths may also be employed in the cooking liquor.

The fibers, fibrillated and cooked as described above are thoroughly washed, mixed with a paper makers clay, and made into mats of the desired thickness, usually about 0.030 inch. It is preferable to build up a mat in several layers as this procedure gives greater uniformity and strength. Eight to ten layers have been found very satisfactory. This can be done by the use of various types of paper machines known to those skilled n the art.

The clay impregnates the entire sheet by filling in the small interstices between the fibers. and the finished mat is strong, flexible and frw'from crevices. It may be dried and stored like ordinary paper stock, and the quality of any batch may be tested out long in advance of the time for usi batch in commercial press room wor To put the sheets or mats in condition for any use it is only necessary to bring up their moisture content in a humidor to that content best suited to the needs of the moment. A moisture content of 10 to before scolzi-ching will be found suitable for most wor A stereotype mat made as above 0 I the even though classifiable as a dry mat and not a wet mat will give clear, deep and sharp impressions having smooth dense surfaces. It may be used for fine linereproductions with much the same results as from the use of a wet matand without any" of the worrying uncertainties incident to wet mat production.

I claim:

1. A stereotype mat composed essentially of fibrillated fibers and a filler; substantially as described.

2. A stereotype mat composed essentially p51 fibrillated cellulose fibers and a mineral er. q

3. A stereotype mat composed of a plurality of superposed layers of fibrillated cellulose fibers, and a filler,

- 4. A stereot pe mat comprising clean ungelatinized fibrillated fibers impregnated with clay.

5. A stereotype mat consisting essentially of clay and fibrillated cellulose fibers freed from gelatinized cellulose by cooking with alkali; substantially as descr bed.

6. A stereotype ,mat comprisin a plurality of superposed layers felte together, each of said layers consisting essentiall of clay and of co lulose fibers that have n fibrillated'bybeating in water and purified 30 of gelatinized cellulose by heating in alkali, substantially as described.

7. The method of making a dry mat which 'nized cellulose and soften the fibrillatedfibers.

9. The method of making a dry mat which .consists in beating cooked wood pulp in water until the fibers separate and develo fibrils, cooking the fibrillated fibers in alka to free the fibers from gelatinous material, washing in water, mixing with clay, forming into sheets composed of a plurality of like layers felted together and allowin said sheet to dry; substantiall as describe In testimony whereof I a x my signa- 55 ture.

ARLIE WILLIAM SOHORGER. 

